1. Field of Invention
The present invention relates generally to antennas, and more particularly, to a hybrid antenna system including a displaceable whip antenna and a concealed antenna configured for use in a portable wireless communications device.
2. Related Art
In recent years, a substantial increase in the use of personal wireless communications devices (WCDs), such as cellular telephones, has fueled a corresponding increase in the need for suitable antennas for the WCDs. A number of important requirements drive the configuration of such an antenna, including low antenna part and manufacturing costs, compact size, omnidirectional gain and suitable frequency bandwidth, high reliability, pleasing aesthetics or appearance, and comfortable ergonomic packaging.
One type of commonly used antenna configuration includes an elongated whip or monopole/dipole antenna. In one known configuration, the whip antenna selectively extends from or retracts into a cellular telephone casing. An extended whip antenna advantageously maintains a relatively uniform omnidirectional gain pattern even when a user holds the cellular telephone near his or her head because the extended whip antenna extends away from the cellular telephone and the user""s head. Therefor, the whip antenna works well in relatively low receive power situations, for example, at the edge of a signal coverage zone or cell. On the other hand, disadvantages arising from the elongate, protruding contour of the whip antenna include a susceptibility to damage and unsightliness to aesthetically sensitive consumers.
Cellular telephones often include a short helical antenna used in conjunction with the whip antenna and activated when the whip antenna is retracted into the casing of the cellular telephone. The helical antenna typically includes a radiator length approximating that of the whip antenna, even though the helical antenna is more compact, more aesthetically pleasing, and less susceptible to damage than the whip antenna. Nevertheless, the helical antenna protrudes substantially and permanently from the cellular telephone so as to adversely impact cellular telephone aesthetics and render the helical antenna susceptible to damage.
Accordingly, cellular telephone manufacturers offer other, more aesthetically pleasing alternatives to the whip and helical antennas, such as an internal antenna housed wholly within and protected by a casing of the cellular telephone. Such an internally mounted antenna permits a cellular telephone manufacturer to construct sleek, aesthetically pleasing, and ergonomically satisfying cellular telephones. Because the internal antenna is encased within the cellular telephone, it works well in relatively high and normal receive signal power situations, but not as well at fringe coverage areas where received signal power is relatively low. Also, while aesthetically more acceptable than the whip antenna, the internal antenna (and the helical antenna mentioned above) suffers adverse antenna gain modification due to antenna loading when the user grasps the casing near the internal antenna, and when the user holds the casing, and thus the internal antenna, near his or her head.
Hence, in an antenna system for a Wireless Communication Device (WCD), there is a need to combine the performance advantages of a whip antenna with the aesthetic and ergonomic advantages associated with an internal antenna, and to mitigate the disadvantages associated with each of these antenna types.
The present invention provides a hybrid antenna system for a portable WCD. The hybrid antenna system includes a concealed, internal shielded substrate antenna fixedly mounted wholly internally within a casing of the portable WCD. The hybrid antenna system also includes a displaceable antenna, such as a whip antenna, that is selectively extendable from and retractable within the casing. The antenna system includes a mechanism for electrically coupling the displaceable antenna to internal RF circuitry of the portable WCD when the displaceable antenna is in an extended position and for electrically isolating the displaceable antenna from the internal RF circuitry when the displaceable antenna is in a retracted position within the casing.
In a first embodiment, the internal antenna is operatively coupled to the RF circuitry when the displaceable antenna is in both an extended operative position and a retracted inoperative position. Thus, the internal and displaceable antennas are operatively connected in parallel and to the RF circuitry when the displaceable antenna is in the extended position, but only the internal antenna is connected to the RF circuitry when the displaceable antenna is in the retracted position.
In a second embodiment, only one of the displaceable and internal antennas is coupled to the RF circuitry at a time. Specifically, only the displaceable antenna is coupled to the RF circuitry when in the extended operative position, and only the internal antenna is coupled to the RF circuitry when the displaceable antenna is in the inoperative retracted position within the WCD casing. The second embodiment includes two antenna switching arrangements. The first arrangement includes a mechanical switch for switching between antennas while the second arrangement includes an electronic switch for switching between antennas.
The electrical coupling may be effected by a direct electrical connection, by inductive or conductive coupling or by other effective means.
Features and Advantages
The hybrid antenna system combines the performance advantages of a whip antenna with the aesthetic and ergonomic advantages associated with a concealed, internal antenna in a portable WCD.
During normal use of the WCD, that is, when signal coverage is relatively good, the whip antenna is retracted, inoperative, and hidden inside the WCD casing. The operative, concealed internal antenna provides satisfactory performance under such conditions. Thus, most of the time, the WCD maintains a sleek, aesthetically pleasing appearance. However, in those instances where signal coverage is poor, the user extends the higher performing whip antenna to effectively combat the poor signal coverage and to thus extend the useable range of the WCD.
The hybrid antenna system is constructed and arranged in a straight forward manner using relatively few, well known components to reduce antenna system manufacturing complexity, cost, and size.